1. Field of the Invention
The present invention relates to a material having a hard coating film formed on a substrate surface thereof, and more particularly a hard-coated material to be used as an item such as a cutting tool, a sliding component part, or a metal die for molding.
2. Description of the Related Art
Conventionally, a hard coating film made of such a substance as TiN (nitride of Ti), TiC (carbide of Ti), TiCN (carbonitride of Ti), TiAlN (complex nitride of Al and Ti), or TiAlCrN (complex nitride of Ti, Al and Cr) is formed on a substrate made of cemented carbide, cermet, or high-speed tool steel for enhancing the wear resistance thereof in the fabrication of cutting tools to be used for such purposes as meal cutting, drilling and end milling, metal dies to be used for such purposes as press molding and forging, and jigs and tools to be used for such purposes as punching and blanking.
For example, in Patent Document 1 indicated below, there is disclosed a hard-coated material to be used as a cutting tool, which is provided with a hard coating film having a component composition represented by the formula (Ti1-a-b-c-d, Ala, Crb, Sic, Bd)(C1-eNe), wherein 0.5≦a≦0.8, 0.06≦b, 0≦c≦0.1, 0≦d≦0.1, 0.01≦c+d≦0.1, a+b+c+d≦1, and 0.5≦e≦1 (where variables a, b, c, and d denote the atomic ratios of Al, Cr, Si, and B respectively, and variable e denotes the atomic ratio of N; the same shall apply hereinafter).
Patent Document 1:
Japanese Unexamined Patent Publication No. 2003-071611
The conventional hard coating film mentioned above has the following disadvantage, however.
In the current metal working by using a cutting tool or jig such as noted above, machining operations are performed at higher speed with higher surface pressure for increasing productivity, and there is a growing trend toward the use of a smaller amount of lubricant in consideration of friendliness to the environment. It is particularly noteworthy that hard coating films are subject to significant wear in today's practice of metal working in which steel workpieces having higher strength are processed.
In the use of a cutting tool or jig such as noted above, when a hard coating film formed on a substrate thereof wears to a certain extent, the hard coating film is selectively dissolved and removed from the substrate by an electrochemical method for the purpose of re-forming a new hard coating film on the substrate. Thus, the substrate having a new hard coating film can be recycled. However, in a situation where a relatively thick hard coating film has been formed on a substrate, it takes a considerable period of time to remove the hard coating film from the substrate, giving rise to a disadvantage in working efficiency. In particular, where a CrN-based coating film featuring superior corrosion resistance has been formed on a substrate for providing sliding wear resistance, it is rather difficult to remove the CrN-based coating film from the substrate, causing a hindrance to substrate recycling.